1. Field of the Invention
The present invention relates generally to apparatus for testing jet engines. In particular, the present invention relates to an annular after reactor (AAR) which is positioned in the exhaust of a jet engine under static test to remove particulate matter and other environmentally unsafe compounds from the exhaust of the jet engine and which includes a sound attenuator for substantially reducing noise associated with the testing of the engine.
2. Description of the Prior Art
The National Ambient Air Quality Standards established by the Clean Air Act requires the removal of fine particle concentrations from the atmosphere in an effort to decrease lung disease and related illnesses as well as mortality rates in urban areas. Currently, the standards have a criteria of PM10 (particles smaller than 10 microns in diameter, however, a standard for PM2.5 is in the process of being imposed. In addition, the Clean Air Act provides for the promulgation of national emission standards for engine test facilities including jet engine test cells.
The emissions of particulate matter, nitrogen oxides (NOX), carbon monoxide and unburned hydrocarbons from the engine exhaust from a jet engine under test has been a concern of the military for two decades, however a cost effective approach for reduction of these environmentally harmful emissions remains to be identified.
Further, the problems that must be addressed to control these emissions are considerable, including the following: (1) the pollutant must be removed from large quantities of engine exhaust as well the augmentation air that accompanies and mixes with the exhaust; (2) the exhaust gases move at velocities of up to 3000 ft/sec and have temperatures of up to 3000 degrees Fahrenheit; (3) the operational conditions of jet engine test cells change frequently so that steady state operation is difficult to achieve; (4) proper test conditions require that only a limited back pressure be developed in the test cell augmentation tube; and (5) the cost for treatment of an exhaust stream from a jet engine is proportional to the total exhaust gas flow and inversely proportional to the pressure drop permitted.
One prior art approach provided for the use of water sprays to remove particulate matter from the jet engine exhaust stream. However, the approach led to the creation of acidic fallout near the jet engine test cell. In addition, the use of water sprays to remove PM2.5 particulates (i.e., particulates of a size less than 2.5 microns in diameter) is generally ineffective since particulates smaller than the order of 2.0 microns tend to follow streamlines around water droplets rather than be collected on them by impaction.
Other prior art approaches such as the use of a filter bed to remove particulate matter from jet engine exhausts have also been shown to be ineffective and costly.
In addition to the problems associated with the removal of particulate matter from jet exhaust, there is currently a need to substantially reduce the noise produced by the jet engines being tested in a static environment.
In the past, jet engine test cells and hush houses for testing jet engines in a static environment were dependent upon containment of the noise generated by the jet engine exhaust plume. Large structures and acoustic materials were used to absorb the acoustic energy. However, these structures are often very expensive and are generally insufficient for reducing to acceptable levels the noise generated by the static testing of jet engines.
Accordingly, there is a need for a relatively simple, cost effective and highly efficient apparatus for the removal of particulate matter and other environmentally harmful compound from the exhaust of a jet engine under test. Further, this apparatus needs to substantially reduce noise generated by the testing of a jet engine in a static environment.
The present invention overcomes some of the disadvantages of the prior art in that it comprises a relatively simple yet highly effective apparatus for removing particulate matter and other environmentally unsafe compounds from the exhaust of the jet engine being tested. In addition, the present invention includes apparatus for substantially reducing noise generated by a jet engine in a static environment such as a jet engine test cell.
An annular after reactor, comprising an embodiment of the present invention, is aligned axially with the direction of exhaust flow from the exhaust port of jet engine. Located near the front end of the annular after reactor is a first set of gas injectors which extend inward into the interior of the after reactor. A second set of gas injectors which are located downstream from the first set of gas injectors also extend inward into the interior of the after reactor. The first set of gas injectors inject natural gas (or other fuel) into the exhaust flowing from the jet engine, while the second set of gas injectors inject ammonia into the exhaust from the jet engine.
The natural gas, when ignited, substantially raises the temperature of the jet engine""s exhaust to a temperature range of between 1850xc2x0 F. to 2200xc2x0 F. and causes the incineration of the particulate matter in the exhaust. Ammonia, when injected into the exhaust stream of the jet engine""s exhaust, functions as a reductant to eliminate up to 90% of the NOX compounds in the exhaust stream.
The annular after reactor also includes a jet engine exhaust buster assembly for substantially reducing noise generated by a jet engine""s exhaust from a jet engine under test in a static environment such as a jet engine test cell.